1. Field of the Invention
The present invention generally relates to balloon catheters, and more specifically relates to balloons for balloon catheters that have improved flexibility and methods for making such balloons.
2. Description of Related Art
Percutaneous transluminal angioplasty (PTCA) is used to open coronary arteries, which have been occluded by a build-up of cholesterol fats or atherosclerotic plaque. Typically, a guide catheter is inserted into a major artery in the groin and is passed to the heart, providing a conduit to the ostia of the coronary arteries from outside the body. A balloon catheter and guidewire are advanced through the guiding catheter and steered through the coronary vasculature to the site of therapy. The balloon at the distal end of the catheter is inflated, causing the site of the stenosis to widen. Dilation of the occlusion, however, can form flaps, fissures or dissections, which may threaten, re-closure of the dilated vessel. Implantation of a stent can provide support for such flaps and dissections and thereby prevent reclosure of the vessel. Reducing the possibility of restenosis after angioplasty may reduce the likelihood that a secondary angioplasty procedure or a surgical bypass operation will be needed.
A stent is typically a hollow, generally cylindrical device formed from wire(s) or a tube, and is deployed in a body lumen from a radially contracted configuration into a radially expanded configuration, which allows it to contact and support the vessel wall. A plastically deformable stent can be implanted during an angioplasty procedure by using a balloon catheter bearing the compressed or “crimped” stent, which has been loaded onto the balloon. The stent radially expands as the balloon is inflated, forcing the stent into contact with the body lumen, thereby forming a support for the vessel wall. Deployment is effected after the stent has been introduced percutaneously, transported transluminally and positioned at a desired location by means of the balloon catheter.
A balloon of appropriate size and pressure may be first used to open the lesion. The process can be repeated with a stent loaded onto a balloon. A direct stenting procedure involves simultaneously performing angioplasty and stent implantation using a stent mounted on a dilatation balloon. After the balloon is withdrawn, the stent remains as a scaffold for the injured vessel.
The overall performance of the balloon may depend on the flexibility and strength of the balloon. If the balloon does not exhibit enough flexibility, the delivery of the balloon and the stent may be impeded, as it may be more difficult to navigate through the torturous path of the vessels if the balloon is too stiff. However, soft balloons with higher flexibility may not have enough hoop strength to effectively open a lesion and/or expand a stent.
It is desirable to provide a stent balloon assembly with a balloon having improved flexibility and enough hoop strength to open a lesion and/or expand the stent.